Tone arm



F. STEVENS May 6 1924;

TONE ARM Filed Dec. 1

aw gm ATTU RNEY.

l atented May 6, 1924.

UNITED STATES FRANK STEVENS, or PHILADELPHIA, PENNSYLVANIA, ASSIGNOR -'ro CHARLES R.

PATENT OFFICE.

KEEGAN, OF PHILADELPHIA, PENNSYLVANIA.

' TONE ARM.

Application filed December 1, 1920. Serial No. 427,619.

on phonographs to convey the reproduced sounds from the sound box totthe horn or amplifier within the cabinet, and itsobjects are to provide a universally movable arm, to eliminate friction in its motions, particu-' larly to the lateral or horizontal motion produced by engagement of the stylus with the sound spiral and to afford other advantages which will appear in the description.

I attain these objects by the mechanism set forth in the following description and the accompanying drawings, in which-- Figure l is a side elevation, mostly in section, of my invention; Figure 2, a plan view at the plane of line 2-2 in Fig. 1, with the portions there-above removed; and, Figure 3, a detail View showing the application of the stabilizing clips.

Similar 'indices refer to similar parts throughout the several views.

The form of my invention here shown is particularly constructed for and designed to be used on a phonograph in which the horn or amplifier (not shown) is concealed within the case of the instrument and beneath the record turn table, but of course, its construction would be necessarily modified to meet the requirements of phonographs in which the amplifier might be located elsewhere.

For the purpose of illustrating my invention I have described and shown in the accompanying drawings one form thereof which is at present preferred by me, although it is to be understood that the various instrumentalities of which my invention consists can be variously arranged and organized and that my invention is not to be limited to the precise form, arrangement, and organization as herein shown and described, and that I hereby reserve the right to reorganize and rearrange these instrumentalities within the scope of my claims.

In this specific form the tone, arm consists of a conical tube, 1, curved at its larger end so as to meet at 2 and be rigidly joined to the upper member, 3, of a partly spherical universal joint." This joint is composed of four principaljparts, the upper member 7 3 just mentioned, its corresponding member 4, ,both of which are movable-#andthe two-plece embracing socket consisting of the vertical support '5, and its annular locking both of which latter members are collar 6, stationary.

The support 5 is shown secured to the cabinet Aof the phonograph by engagement of threads 7 with corresponding threads in-the collar 8, which is screwedto the cabinet at 9.; e v I The juxtaposed annular plane faces of members 3 and 4 lie at -the equator. of the sphere which they jointly partly form, and they approach each other as closely as is mechanically, possible without touching. They are held apart by the steel balls 10, circularly disposed, so that the upper member 3'is free to be rotated independently of the lower portionL- This lower-member is spherical to a sulficient extent to admit of ample universal motion in ,the'support 5 to answer all practical purposes, and the'upper member 3, resting upon the balls 10, is likewise of equal and similar partially spherical form to permit of ample universal rotation within said support 5 and the collar 6, by

which itis confined and secured incontact with the balls when the collar is held securely in place, by threads 14. As the contactingspherical surfaces of-all four mem-' bers are ground perfectly true, it is evident that the arm 1 may be universally, moved horizontally for a complete circle-and vertically for a sufiicient arc to, meet all requirements. But as it is most desirable that 1 all horizontal motion be as free as possible from resistance of any nature, it has been found of immense advantage to divide the large ball as described and to introduce the small ball bearing construction. This is particularly the case where the phonograph is to be synchronized with some other instrument or mechanism, for the reason that but extremely little resistance to lateral progress of the stylus is required to cause it to jump whereby, obviously, the continuity of the sound production is broken and synchrony lost. Another decided advantage is that this construction permits'of a sound passage free from lateral cracks or openings with the least friction, whereby loss of volume or deleterious alteration of the tones is eliminated.

' The reproduced sounds pass through channel 11 in the tube 1 into channels 11 11 and 11", respectively, formed through the memhers 3, 4; and 5, in succession, and thence into channel 11 which communicates with the horn or amplifier .within; the cabinet.

It will be observed that while the contour of the exterior of the tone arm is partly spherical in form, the sides of the interior channel are in straight lines so that there can be no distortion of the sound waves due "to lateral irregularities. I i

The normal adjustment of the parts is as shown with the lower orifice of 11* alined with the sides of channel 11 so the continuity of the sides will be unhroken when the stylus is resting upon the record. In order to provide for slight inequalities in dimensions of various cabinets, the shoulder or flange of the collar Q'may be countersunk into the shelf or support in the cabinet or, conversely, a metal washer of required thickness may be interposed, as the occasion require.

may i V.

11 order to preserve the poise of the.

arm, thereare attached at 12 to the upper memberB, two stabilizing clips, 13, the lower tips of, which are arc shaped and just clear contact with the upper surface of the locking collar 6 when the arm is in normal balance. These stabilizers are located at op,- posite extremities of the diameter of the arm which is perpendicular to the axis of the tube 1.

The operation of the device is such that when the arm is raised from the record the two convex spherical zones of the four-piece joint are called into action, but when the arm is rotated in a horizontal plane the ball bearings 10 come into play and not only eliminate most of the friction but also serve to confine the motion and weight of the portions moved to members 1 and 3, permitting the member 4 to remain inert. Thus,

the weight of the entire movable portion of the arm being carried by the lower member 5 of the socket, within which the greater part of: the spherical contact is made, there can be no friction due to pressure of gravity between the globular portions of member 3 and collar 6, it is evident that the in tion, an elbow shaped sound conductor, a L

hemispherical extension thereto, a movable hemispherical and tubular member, similar to said extension, and means to retain said extension and said member in independently movable, but closed sound conducting alinement.

2. A tone arm cpmprising, in combination, an elbow shaped sound conductor, a hemispherical extension thereto, a fixed support, a concave tubular socket fixed thereto, a movable hemispherical and tubular member similar to said extension reposing in said socket, and means to movably' connect said conductor and said socket in closed sound conducting alinement.

3. In a tone arm, in combination, atwo part spherical bearing, a two part hollow spherical support therefor, theline of contact of the parts of said bearing and the line of contact of the parts of said support being normally on the equatorial line of the bearing whereby both parts of said bearing move together for vertical oscillation, but only one part moves for horizontal oscillation.

Signed at Philadelphia, this fourth day of November, A. D. 1920.

FRANK STEVENS. 

